Combinations of intersecting transverse, coronal, and saggital acquisition planes may be used in TrueFISP (True Fast Imaging with Steady State Precession) magnetic resonance imaging (MRI). For example, intersecting acquisition planes facilitate anatomical localization, facilitate MRI guided interventions, facilitate imaging freely moving subjects, and so on. However, saturation artifacts have conventionally been associated with intersecting acquisition planes. These saturation artifacts may include saturation banding that is distinct from the well known TrueFISP off-resonance banding artifacts. Thus, previous attempts at mitigating off-resonance banding artifacts may be irrelevant to mitigating saturation artifacts associated with intersecting acquisition planes. Intersection saturation banding may involve areas of low signal or signal attenuation at intersections of orthogonal imaging planes. Artifacts are associated with signal intensities that are unrelated to the spatial distribution of the object being imaged.
Interventional MRI (IMRI) may employ TrueFISP acquisitions for multiplanar guidance. The multiplanar guidance may be affected by the intersection saturation artifacts that occur at the intersections of the multiple planes. FIG. 7 illustrates a conventional TrueFISP pulse sequence. In coherent steady-state sequences, transverse magnetization may be left over after the data acquisition period. Therefore, coherent steady-state sequences may include rewinding the transverse magnetization by reversing the sign of the gradient pulses. In FISP (fast imaging with steady precession), only the phase-encode gradient is rewound. In TrueFISP, which may also be referred to as balanced Fast Field Echo (bFFE)), the sequence has balanced, rewinding gradients in all three directions.
Barker and Williams described interleaving acquisitions in Improving Resolution in MRI by Interleaving Data Acquisition for Increased Digitization Rates, Volume 25, No. 2, Magnetic Resonance in Medicine, pg 334-336 (1992). Interleaving involves arranging things in or as if they were in alternate layers. Interleaving can be used to improve acquisition time. U.S. Pat. No. 6,795,723 describes interleaved phase encoding acquisition. Butts, et al. also discuss interleaving in Interleaved Echo Planar Imaging on a Standard MRI System, Volume 31, No. 2, Magnetic Resonance in Medicine, pg 67-72, (1994). While interleaving may have been associated with improved acquisition time, it has not been associated with mitigating saturation artifacts that occur at the intersections of multiple planes.